EUGENE, Ore. -- Tyson Gay went down Saturday and the question is when he will be able to get back up.

One week after setting the American record in the 100 meters and also running that distance faster than anyone else ever has, Gay's quest to double up at the Olympics in the 200 ended prematurely and painfully during a quarterfinal heat when he collapsed due to what was described as a "severe cramp" in his left hamstring.

Gay pulled up about a dozen strides into the race, after perhaps 40 meters. He collapsed to the ground and lay there as his competitors raced ahead and a stunned Hayward Field crowd went silent. Officials quickly brought a modified stretcher onto the track and wheeled him to the medical tent for examination.

"Before I went out on the track I felt a little tightness in my hamstring. So I had kind of a bad feeling," Gay said through his promotional agency. "When I came off the curve the first two steps were fine, and then I felt it, sort of a pull, about 40 meters in. Once I was on the ground it didn't hurt as much as when it happened."

Gays's personal physiotherapist , Benny Vaughn, said they would observe the hamstring for 48 hours, but that it was likely Gay could run the 100 in Beijing. Gay said he felt the cramp in the same place as when he cramped during the 2004 Olympic trials which cost him a chance in the Athens Games.

Gay has already qualified for the 100 meters and 400 relay team. But the defending world champion is ineligible to run the 200 -- his best event -- in the Olympics because he did not finish in the top three here. Such is the nature of the Trials.

Tyson Gay was carted off the field after suffering a severe hamstring cramp in his left leg during his 200-meter quaterfinals heat Saturday at the U.S. track trials. AP Photo/David J. Phillip

"It's tough," said Wallace Spearmon, who qualified for the 200 final. "You can be the best athlete coming in but wind up spending the Olympics home on the couch. But I don't know any way else you can do it."

Gay's collapse opened a door for someone else to make the Olympic team but it also cast a shadow of vulnerability over the remaining heats. Spearmon noted that times were a little slower than they might otherwise be the rest of the day.

"Anytime you see that, that's a red flag," Spearmon said. "You say to yourself, 'Be careful. Make sure you stretch.' That's nothing you want to see. I wouldn't wish that on my worst enemy. Hopefully it's just a cramp but I'm not a doctor."

There was some speculation that Gay's blistering runs in the 100 last weekend -- in addition to breaking the American record last Saturday, his wind-aided run last Sunday surpassed Obadele Thompson's mark for the fastest in history -- might have taken a toll on his body. Spearmon said that running the 100 takes more out of him than the 200.

"My toes were sore, my neck was sore my ears were sore, my whole body was sore. That's a tough event," he said. "And then to double up with the 200? Man. When Obadele ran a (wind-aided) 9.69, he said his body was never the same. I hope that's not the case with Tyson."

Gay's mother, Daisy Gay Lowe, said her son was upset tearful after the injury, but that his spirits lifted.

"He just needed some reassurance," she said. "I prayed for him and prayed over him, and just wanted to make sure he didn't get too down." She wore a shirt with her son's face on it. And below, there was an Adidas logo and the slogan, "Impossible is Nothing."

"It's going to work out," she said. "It's going to be OK. He's going to run the 100, and he's going to win the 100, and he's going to run in the 4x100 relay. It's all right."

Added Tim Lowe, Gay's stepfather, "He'll be back. Now he can concentrate on the 100, and being the fastest man in the world, which is who he is."

Former Olympic decathlete Dan O'Brien said that if Gay wakes up tomorrow and is able to stretch out, he'll be fine, but if he is so sore he can't "sit on the toilet" he could be in trouble. If it is indeed just a severe cramp, O'Brien said Gay could be running again in three days. If there is an injury to the hamstring, he said it is possible he could be back for the Olympics depending on the severity.

"It's a tough week, these are real trials," O'Brien said. "This is really what separates the world champions, the Olympic champions, the medalists, to be able to get through the rounds. We know guys on the European circuit and every two weeks they can run a 10 flat. Those guys don't seem to come to the trials and get it done round after round after round.

"This may make him more determined and more focused in the single event in Beijing."

Luke Cyphers is a senior writer for ESPN The Magazine and Jim Caple is a senior writer for ESPN.com.